Re: Measuring Current Output of MOT's?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Chris Fanjoy" <zappyman-at-hotmail-dot-com> 

 >
 >Kinda and yes - Don't bother with the resistors, just have a meter
 >with a fast response time and short the output through the ammeter
 >section your meter.  Have it insulated from ground, though a high
 >voltage *shoudln't* appear across it unless one of the leads lets go
 >(specifically the ground lead).  A better way would be to use a
 >clamp on meter with the transformer lead shorted and a decent amount
 >of insulation - just in case.
 >
 >A few tips - 1) I said fast response cause chances are you're going
 >to blow a breaker, 2) DON'T HOLD THE METER!!!! 3) The MOT will heat
 >up, so don't do this too long, but run it at a full 120 in if that's
 >how you're going to be running it on a TC (ie not 2 primaries in
 >series).
 >
 >The reason your resistor method didn't work is because the current
 >output will be drastically different at 10V compared to 120V in, and
 >at 300 mA, you're asking the resistors to dissipate almost 20W, and
 >the MOT is capable of a lot more than 300 mA - usually over 1A if
 >not ballasted in any way, and with 1A, the resistor will dissipate
 >190W each!!

This is kind of what I suspected. I guess I won't bother trying to figure 
out the current output of an MOT, instead I'll have to rely on on things 
such as voltage doublers, spark gap width (and tank cap value), etc for 
higher output voltage.

Today I came up with what I thought was a brilliant idea - carefully bend 
out one of the loops of the primary winding on an MOT, cut it, and attach a 
wire. The theory being, to use only a small part (say, 1/4) of the primary 
winding, to create a much higher input-output ratio. I first located an old 
MOT that was rather beat up, but electrically good. It was surprisingly 
easy to bend out one of the loops and splice in a lead wire. When powered 
with 10 V from the Variac, it measured almost 500 VAC, meaning that at 120V 
input it should put out roughly 6000V! Congratulating myself on the 
apparent success of this experiment, I removed the meter leads and cranked 
the Variac all the way up. The resulting loud buzz and (seconds later) 
blown circuit breaker, revealed what was obviously a serious flaw in this 
idea! Obviously I've either forgotten (or just never properly learned) some 
fundamentals of transformer design. Now I'm wondering if it's possible to 
unweld the core! of an MOT, and replace the secondary with a homemade one. 
Since I don't have access to welding / cutting equipment, I won't get to 
test this theory anytime soon.

Thanks anyway for the advice.

 >
 >Hope this helps, please play safe with MOTs, they can kill you
 >pretty easily!
 >
Yeah I'm aware of that, and I handle these things pretty carefully....